U.S. patent number 4,364,128 [Application Number 06/297,996] was granted by the patent office on 1982-12-21 for artificial foot.
This patent grant is currently assigned to Jobst Institute, Inc.. Invention is credited to Thomas A. Mummert.
United States Patent |
4,364,128 |
Mummert |
December 21, 1982 |
Artificial foot
Abstract
An artificial foot for attachment to a prosthetic device
securable to a leg stump. The artificial foot is adjustable in
length and in height of the instep so as to permit the foot to be
snugly inserted in a conventional shoe. The artificial foot
includes a simulated toe portion which is horizontally pivotally
connected to a sole plate. A spring-pressed linkage normally
maintains the simulated toe portion in an aligned position with the
sole plate, but permits upward pivotal movement of the toe portion
in response to the forces encountered in taking a step. A latching
lever frictionally engages the spring-pressed linkage to latch the
pivoted toe portion in its upward position during that portion of
the step wherein the weight is carried by the other foot. The
artificial foot is connected to the bottom plate of a prosthetic
device by a plurality of cushion plugs. The rearmost one of the
cushion plugs mounts a depending plunger which is operatively
connected with the latching lever to release same when the heel
portion of the artificial foot first engages the ground at the end
of a step, thereby permitting the simulated toe portion to resume
its aligned position.
Inventors: |
Mummert; Thomas A. (Toledo,
OH) |
Assignee: |
Jobst Institute, Inc. (Toledo,
OH)
|
Family
ID: |
23148555 |
Appl.
No.: |
06/297,996 |
Filed: |
August 31, 1981 |
Current U.S.
Class: |
623/53; 623/38;
623/49; 623/50 |
Current CPC
Class: |
A61F
2/66 (20130101); A61F 2002/5073 (20130101); A61F
2002/5009 (20130101); A61F 2/6607 (20130101) |
Current International
Class: |
A61F
2/60 (20060101); A61F 2/66 (20060101); A61F
2/50 (20060101); A61F 001/08 () |
Field of
Search: |
;3/6-7,21,23,30-35 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Frinks; Ronald L.
Attorney, Agent or Firm: Wilson, Fraser, Barker &
Clemens
Claims
What is claimed is:
1. An artificial foot adapted for insertion in a conventional shoe
comprising, in combination: a sole plate insertable in the bottom
portions of a shoe, a toe simulator element having its rear portion
horizontally pivoted to said bottom plate, upstanding means secured
to said sole plate for simulating the ankle portions of a foot, a
leg force receiving plate secured to the top portions of said
upstanding means, a prosthesis attachable to the leg stump and
having a bottom plate disposed in generally parallel, overlying
relation to said leg force receiving plate, resilient cushion means
interconnecting said plates but permitting limited pivotal movement
of said prosthesis plate relative to said leg force receiving plate
as a consequence of walking movement of the leg stump, a
spring-pressed linkage operable between said sole plate and said
toe simulator to resiliently urge said toe simulator to a generally
aligned position relative to said sole plate, latching means
normally securing said linkage against movement, and means
responsive to the pivotal movement of said prosthesis plate
relative to said leg force receiving plate as the shoe strikes the
ground in the step for initially releasing said latching means to
permit pivotal movement of said toe simulator to said aligned
position and subsequently latching said linkage in an upward
position of said toe simulator as the step progresses.
2. An artificial foot adapted for insertion in a conventional shoe
comprising in combination: a channel shaped sole plate insertable
in the bottom portions of a shoe and having laterally spaced
upstanding wall portions, a toe simulator element having its rear
portion horizontally pivoted to said bottom plate side walls,
upstanding plate means for simulating the ankle portions of a foot,
means on said upstanding plate means for contacting the inner heel
portions of the shoe, longitudinally adjustable means for
connecting said upstanding plate means to said sole plate, thereby
permitting length adjustment of the artificial foot, a leg force
receiving plate secured to the top portions of said upstanding
plate means, a prosthesis attachable to the leg stump and having a
bottom plate disposed in generally parallel, overlying relation to
said leg force receiving plate, resilient cushion means
interconnecting said plates but permitting limited pivotal movement
of said prosthesis plate relative to said leg force receiving plate
as a consequence of walking movement of the leg stump, a
spring-pressed linkage operable between said sole plate and said
toe simulator to resiliently urge said toe simulator to a generally
aligned position relative to said sole plate, latching means
normally securing said linkage against movement, and means
responsive to the pivotal movement of said prosthesis plate
relative to said leg force receiving plate as the shoe strikes the
ground in a step for initially releasing said latching means to
permit pivotal movement of said toe simulator to said aligned
position and subsequently latching said linkage in an upward
position of said toe simulator as the step progresses.
3. An artificial foot adapted for insertion in a conventional shoe
comprising in combination: a channel shaped sole plate insertable
in the bottom portions of a shoe and having laterally spaced
upstanding wall portions, a generally U-shaped toe simulator having
its rear portion horizontally pivoted to said upstanding wall
portions, a pair of laterally spaced, vertical side plates rigidly
interconnected at their rear by a transverse plate portion, means
on said transverse plate portion for contacting the inner heel
portions of the shoe, longitudinally adjustable means for
connecting said side plates to said sole plate, thereby permitting
length adjustment of the artificial foot, a leg force receiving
plate secured to the top portions of said side plates, a prosthesis
attachable to the leg stump and having a bottom plate disposed in
generally parallel, overlying relation to said leg force receiving
plate, resilient cushion means interconnecting said plates but
permitting limited pivotal movement of said prosthesis plate
relative to said leg force receiving plate as a consequence of
walking movement of the leg stump, a spring-pressed linkage
operable between said sole plate and said toe simulator to
resiliently urge said toe simulator to a generally aligned position
relative to said sole plate, latching means normally securing said
linkage against movement, and means responsive to the pivotal
movement of said prosthesis plate relative to said leg force
receiving plate as the shoe strikes the ground in a step for
initially releasing said latching means to permit pivotal movement
of said toe simulator to said aligned position and subsequently
latching said linkage in an upward position of said toe simulator
as the step progresses.
4. An artificial foot adapted for insertion in a conventional shoe
comprising in combination: a channel shaped sole plate insertable
in the bottom portions of a shoe and having laterally spaced
upstanding wall portions, a generally U-shaped toe simulator having
its rear portion horizontally pivoted to said upstanding wall
portions, a pair of laterally spaced, vertical side plates rigidly
interconnected at their rear by a transverse plate portion, means
on said transverse plate portion for contacting the inner heel
portions of the shoe, longitudinally adjustable means for
connecting said side plates to said sole plate, thereby permitting
length adjustment of the artificial foot, a transversely curved
plate simulating the instep surface of the foot, means for
supporting said instep plate in overlying relation to said sole
plate, a leg force receiving plate secured to the top portions of
said side plates, a prosthesis attachable to the leg stump and
having a bottom plate disposed in generally parallel, overlying
relation to said leg force receiving plate, resilient cushion means
interconnecting said plates but permitting limited pivotal movement
of said prosthesis plate relative to said leg force receiving plate
as a consequence of walking movement of the leg stump, a
spring-pressed linkage operable between said sole plate and said
toe simulator to resiliently urge said toe simulator to a generally
aligned position relative to said sole plate, latching means
normally securing said linkage against movement, and means
responsive to the pivotal movement of said prosthesis plate
relative to said leg force receiving plate as the shoe strikes the
ground in a step for initially releasing said latching means to
permit pivotal movement of said toe simulator to said aligned
position and subsequently latching said linkage in an upward
position of said toe simulator as the step progresses.
5. An artificial foot in accordance with claim 1, 2, 3 or 4 wherein
said latching means comprises a lever pivoted at one end to said
sole plate and having a slot frictionally traversed by said linkage
means, whereby the application of a downward force to the
non-pivoted end of said lever frees the frictional bind on said
linkage means, and said means responsive to the pivotal movement of
said prosthesis plate comprises an elastomeric mass disposed
between said prosthesis plate and said leg force transmitting plate
and a plunger dependingly secured in said elastomeric mass and
freely traversing said leg force transmitting plate to contact the
non-pivoted end of said lever.
6. An artificial foot in accordance with claim 1, 2, 3 or 4 wherein
said latching means comprises a lever pivoted at one end to said
sole plate and having a slot frictionally traversed by said linkage
means, whereby the application of a downward force to the
non-pivoted end of said lever frees the frictional bind on said
linkage means, and said means responsive to the pivotal movement of
said prosthesis plate comprises an elastomeric mass disposed
between said prosthesis plate and said leg force transmitting
plate, a plunger dependingly secured in said elastomeric mass and
freely traversing said leg force transmitting plate to contact the
non-pivoted end of said lever, and a stop member adjustably secured
to said depending plunger to pickup the rear portion of said leg
force transmitting plate during the portion of the step wherein the
heel portion of the artificial foot must be elevated.
7. An artificial foot in accordance with claim 3 where said
longitudinally adjustable means comprises opposed longitudinaly
slots in each of the bottom portions of said side wall, the bottom
edge of each said slot having a plurality of longitudinally spaced
vertical recesses therein, a pair of transversely aligned holes
respectively provided in said upstanding wall portions, opposed
pairs of said recesses being selectively alignable with said holes
as said side plates are longitudinally adjusted relative to said
sole plate, and rod means transversing said holes and a selected
opposed pair of recesses, thereby adjusting the effective length of
said artificial foot.
8. An artificial foot in accordance with claim 7 wherein said rod
means comprises a U-shaped rod having each free end portion
laterally outturned to respectively traverse a selected recess and
one of said holes, and a transversely curved plate simulating the
instep surface of a foot, said plate being supported in part in
overlying relationship to said sole plate by the bight portion of
said U-shaped rod, whereby the vertical position of said
transversely curved instep plate varies directly with the effective
length of the artificial foot.
9. An artificial foot in accordance with claim 1, 2, 3 or 4 wherein
said resilient cushion means comprises at least four equi-spaced
elastomeric blocks secured between said prosthesis plate and said
leg force receiving plate, thereby permitting limited relative
pivotal movement of said plates about a plurality of horizontal
axes.
10. An artificial foot adapted for insertion in a conventional shoe
comprising, in combination: a sole plate insertable in the bottom
portions of a shoe, upstanding means secured to said sole plate for
simulating the ankle portions of a foot, means for attaching said
ankle simulating means to a prosthesis attachable to the leg stump,
an instep simulating member, linkage means for positioning said
instep simulating member in a plurality of vertical positions
relative to said sole plate, means for longitudinally varying the
point of securement of said ankle simulating means to said sole
plate to change the effective length of the artificial foot, and
means responsive to said last mentioned means for varying the
vertical position of said instep simulating means in direct
proportion to the effective length of the artificial foot.
11. An artificial foot adapted for insertion in a conventional shoe
comprising, in combination: a sole plate insertable in the bottom
portions of a shoe, upstanding means secured to said sole plate for
simulating the ankle portions of a foot, a leg force receiving
plate secured to the top portions of said upstanding means, an
instep simulating member, a first linkage interconnecting said
instep simulating member and said ankle simulating means, a second
linkage interconnecting said instep simulating member and said sole
plate, and means for longitudinally adjusting the point of
securement of said ankle simulating means and said sole plate to
change the length of the artificial foot and concurrently raise the
position of the instep simulating member.
12. An artificial foot in accordance with claim 10 or 11 wherein
said means for longitudinally adjusting the point of securement of
said ankle simulating means and said sole plate comprises a
horizontal hole in one of said sole plate and said ankle simulating
means and a plurality of longitudinally spaced recesses in the
other of said sole plate and said ankle simulating means, a pin
traversing said hole and a selected one of said recesses to
longitudinally fix said ankle simulating means relative to said
sole plate, and means connecting said pin to said instep simulating
means.
13. An artificial foot in accordance with claim 10 or 11 wherein
said sole plate as a channel shaped configuration including a pair
of laterally spaced side walls and said ankle simulating means
comprises a pair of laterally spaced upstanding plate slidable in
the channel defined by said sole plate, a transverse hole extending
through both side walls of said sole plate, thereof transversely
aligned longitudinally extending slots respectively provided in the
bottom portions of said ankle plates and alignable with said
transverse holes, a plurality of longitudinally spaced vertical
recesses along the bottom edge of each of said longitudinal slots,
a generally U-shaped rod having the free end portions thereof
laterally outturned and respectively engagable with a selected one
of said recesses and the adjacent hole in said sole plate side
walls, and means for pivotally securing the bight portion of said
U-shaped rod to said instep simulating means.
Description
FIELD OF THE INVENTION
This invention relates to an artificial foot for attachment to a
prosthetic device securable to a leg stump, and particularly to an
artificial foot which can be temporarily employed following surgery
and which accomodates the mounting thereon of the patient's normal
shoe.
HISTORY OF THE PRIOR ART
There are literally hundreds of prior patents dealing with
artificial feet for patients who suffer the severance of portion of
a leg. While there are many prior art prosthetic devices attachable
to the leg stump which are satisfactory for permanent use by a
patient once his recovery has been established, such devices
require custom manufacture and fitting which involves a substantial
delay in making the patient ambulatory. There is a distinct need
for an economical artificial foot which may be inserted into the
patient's regular shoe, but at the same time provide the required
flexibility of movements normally associated with walking so that
when attached to the limb stump by a prosthetic device, the patient
may become ambulatory at a much earlier stage in his recovery. The
psychological value of letting the amputee relearn to walk in his
own shoes cannot be over estimated.
Such artificial foot must necessarily incorporate a cushion
connection to the prosthetic device and also permit the normal
upward flexure of the toe portion of the artificial foot that is
encountered when walking naturally. Moreover, it is most important
that the toe portion of the artificial foot be latched in its
upwardly pivoted relationship to the remainder of the foot during
that portion of the step wherein the patient's weight is carried by
the other leg, to prevent the toe of the shoe from dragging along
the ground, which would necessitate the patient adopting a limp in
order to overcome such dragging motion. Additionally, as the heel
of the shoe containing the artificial foot strikes the ground at
the end of a step, it is desirable that the simulated toe portion
of the artificial foot be automatically moved downwardly to its
horizontally aligned position with respect to the sole portion of
the artificial foot so that the shoe containing the artificial foot
is in flat engagement with the ground when the entire weight of the
patient is supported by the amputated leg.
If the patient's normal shoe is to be employed in conjunction with
the aritifical foot, it necessarily follows that the artificial
foot must incorporate some means for adjusting the effective length
of the artificial foot and also the height of the instep surface of
the artificial foot in order to permit the patient's shoe to be
securely and neatly fastened to the artificial foot.
Although the voluminous prior art incorporates disclosures of
artificial feet having a simulated toe portion pivoted to a sole
portion, the automatic control of the position of such toe portion
through utilization of forces normally imparted to the artificial
foot during walking, has not been disclosed in the prior art.
SUMMARY OF THE INVENTION
This invention provides an artificial foot adapted to be inserted
in the amputee's normal shoe and to be adjustable to snugly fit the
salient interior portions of such shoe, such as the end of the toe,
the heel and the instep.
A sole plate is provided having means at the front end thereof for
horizontally pivotally mounting a member simulating the toes of the
foot. A control linkage is provided, including a stretched spring,
for urging the toe simulating portion of the device to its normal
position of horizontal alignment with the sole portion of the
artificial foot. A pair of upstanding side plates are provided
which are integrally connected by a transverse heel portion. An
elastomeric bumper is secured to the transverse heel portion to
bear against the internal surface of the heel portion of the shoe.
To provide a snug fitting of the artificial foot in the patient's
normal shoe, the side plate elements are longitudinally adjustably
mounted to the sole plate so as to lengthen or shorten the distance
of the heel bumper to either the simulated toe portion or to a
simulated ball element provided on the bottom of the sole plate to
conform to the interior longitudinal dimension of the patient's
shoe.
The top walls of the side plates are bent outwardly and rigidly
secured to a circular leg force receiving plate. Such plate is in
turn connected by a plurality of elastomeric plugs to a disc shaped
plate forming the bottom element of a prosthetic device engagable
with the limb stump. At least four equally peripherally spaced
elastomeric plugs are provided, so as to permit cushioned pivotal
movement between the prosthetic plate and the leg force receiving
plate about a plurality of horizontal axes. Two of the
aforementioned elastomeric plugs are disposed in longitudinal
alignment with the longitudinal center axis of the artificial foot
and the other two are transversely disposed. The rearmost plug is
most compressed during that portion of a step wherein the heel of
the shoe containing the artificial foot first strikes the ground.
The degree of compression of the rearmost plug is gradually reduced
and is transferred to the forward plug as the toe portion of the
shoe containing the artificial foot is pivoted relative to the sole
of the foot to accomodate the raising of the heel portion from the
ground. A depending plunger is attached to the rearmost plug and is
downwardly shiftable by the compression of such plug due to the leg
forces applied thereto by the prosthetic plate.
A latch is provided comprising a pivoted lever having a slotted
frictional engagement with the control linkage which imparts a
pivotal bias to the toe portion of the artificial foot. The
nonpivoted end of the lever is disposed in the path of the
depending plunger and is pivoted thereby to a position releasing
the frictional drag of the lever slots on the control linkage, thus
permitting the toe simulating portion of the artificial foot to
return to its horizontally aligned position as the heel of the shoe
containing the artificial foot strikes the ground at the end of a
step. The toe simulating portion is, however, free to pivot
upwardly relative to the sole portion against the bias of the
retaining spring as the artificial foot is rocked forward to
elevate the heel during the next phase of the step. As the heel is
elevated, the compressive forces on the rearmost plug are released,
and the depending plunger is withdrawn from engagement with the
friction lever, which then assumes a binding position with respect
to the simulated toe control linkage and holds the simulated toe in
its upwardly pivoted position until the completion of the next step
with the amputated limb.
Further objects and advantages of the invention will be readily
apparent to those skilled in the art from the following detailed
description, taken in conjunction with the annexed sheets of
drawings, on which is shown a preferred embodiment of the
invention.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a vertical sectional view of an artificial foot embodying
this invention with the elements thereof shown in the positions
occupied as the heel of the shoe containing the artificial foot
first strikes the ground.
FIG. 2 is a view similar to FIG. 1 but showing the elements of the
artificial foot in the positions occupied when the heel portion of
the shoe containing the artificial foot has left the ground at the
initiation of a step by the amputated limb.
FIG. 3 is an exploded perspective view of the artificial foot
illustrated in FIGS. 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, the numeral 10 indicates an artificial
foot assembly constructed in accordance with this invention and
illustrated in FIGS. 1 and 2 in an inserted relationship to a
conventional shoe 1 which, for psychological reasons, is preferably
one of the patient's shoes for the foot that has been removed by
amputation.
As best shown in the exploded view of FIG. 3, the artificial foot
assembly 10 comprises a channel shaped sole plate 11 having
transversely spaced upstanding wall portions 11a and 11b. The
dimensions of sole plate 11 are such that is may be freely inserted
to lie in the bottom portions of the shoe 1. If desired, a pair of
depending cushion elements 12 may be secured to the forward
portions of sole plate 11 by bolts 12a and nuts 12b at the location
corresponding to the ball of a natural foot.
The extreme forward end of sole plate 11 is of reduced lateral
extent, as indicated at 11c, and is provided at its lateral
extremities with upstanding lugs 11d. Such lugs are apertured to
receive a pivot mounting pin 13 for effecting the horizontal
pivotal mounting of a generally U-shaped toe simulator element 14.
Toe simulator element 14 extends into those portions of the shoe 1
normally occupied by the toes.
At the rear end of toe simulator 14, a pair of upstanding ears 14a
are provided, which respectively receive the laterally bent ends
15a of a U-shaped control linkage element 15. Element 15 extends
rearwardly in generally parallel relationship with the sole plate
11 and is urged forwardly by a tension spring 16. One end of spring
16 is secured to a re-entrant portion 15c formed in the bight
portion 15b of the control link 15 and the other end of spring 16
is secured to an upstanding flange 11e punched from the sole plate
11. It is therefore apparent that the toe simulator 14 is
resiliently urged to a position of horizontal alignment with the
sole plate 11 or, in other words, to the position simulating the
configuration of the foot when the amputated leg is at rest in a
standing position, as specifically illustrated in FIG. 1. The toe
simulator 14 is, however, free to pivot upwardly relative to the
sole plate 11 and hence assumes the position illustrated in FIG. 2,
which corresponds to the position of a normal foot when the heel is
elevated as a consequence of taking a forward step by the other
leg.
The artificial foot assembly 10 further includes a pair of
upstanding, laterally spaced, ankle simulating plates 20 and 21.
The bottom edges of ankle plates 20 and 21 respectively rest on the
sole plate 11 adjacent to the sole plate side walls 11a and 11b
respectively. Ankle plates 20 and 21 are integrally connected by a
transverse heel plate 22 which mounts an appropriate resilient heel
cushion 23 by a bolt 23a and cooperating nut 23b.
To provide a snug fit of the artificial foot 10 within the
patient's normal shoe 1, adjustment of the effective length of the
artificial foot is provided by a pair of longitudinally extending
slots 20a and 21a respectively provided in the ankle plates 20 and
21 adjacent the rear ends thereof and lying in close proximity to
the sole plate 11. Slots 20a and 21a are respectively provided with
a plurality of vertical recesses 20b and 21b in the lower slot
surfaces. Such recesses may be successively aligned with
transversely aligned holes 11f and 11g respectively provided in
rearward extension of the sole plate side walls 11a and 11b by
moving the ankle plates 20 and 21 longitudinally relative to sole
plate 11. The effective length of the artificial foot 10 may then
be adjusted by passing a retaining pin through the sole plate side
wall holes 11f and 11g and through any selected aligned pair of
recesses 20b and 21b provided in the ankle plates 20 and 21.
Instead of using a transverse pin to effect such adjustment of the
length of the artificial foot 10, this invention provides a
generally U-shaped rod 24 having outturned lateral extremities 24a
and 24b which respectively engage the sole plate holes 11f and 11g
and a selected aligned pair of ankle plate recesses 20b and 21b.
The length adjustment can then be accomplished without removing the
rod extremities from the side plate holes by pivoting sole plate 11
to move the rod extremities 24a and 24b into the upper part of
slots 20a and 21a, then sliding the sole plate 11 relative to ankle
plates 20 and 21.
The bight portion 24c of the U-shaped rod 24 is then employed to
support a transversely curved plate 25 which simulates the top
surface of the instep portion of the foot, i.e., that portion of
the foot overwhich the laces of a shoe are normally located. The
instep plate 25 is additionally supported in overlying relationship
to the sole plate 11 by a second U-shaped support loop 26 which has
outturned lateral extremities 26a and 26b respectively mounted in
aligned holes 20c and 21c respectively provided in the forward ends
of ankle plates 20 and 21. The bight portions 24c and 26c of the
support loops 24 and 26 are respectively pivotally secured to the
underside of the instep plate 25 by a U-shaped clamp element 27,
which in turn is secured to the instep plate 25 by a pair of bolts
27a.
With the described construction, it will be apparent that the
vertical position of the instep plate 25 will be shifted vertically
in direct proportion to the selected length of the artificial foot
10. As the support rod 24 is moved forwardly along the ankle plate
recesses 20b and 21b, which corresponds to effectively lengthening
the artificial foot 10, the instep plate 25 will be elevated
relative to the sole plate 11. The tight lacing of the shoe 1 over
instep plate 25 snugly secures shoe 1 to the artificial foot 10.
Thus, the construction of this invention provides an automatic
contouring of the artificial foot 10 to snugly conform to the
patient's shoe over a normal range of sizes for a man. Smaller
overall designs would be required to accomodate womens or childrens
shoes.
The top portion of each ankle plate 20 and 21 is provided with a
laterally outturned flange 20d and 21d respectively. Such flanges
are rigidly secured to a disc shaped plate 30 by bolts 29. Plate
30, which hereinafter will be referred to as the leg force
receiving plate, is in turn secured to a prosthesis plate 40 which
forms the bottom element of a prosthetic device (not shown) which
is conventionally secured to the remaining limb of the patient.
Such prosthetic device may comprise any one of a number of such
devices that are currently manufactured and sold. It will be
understood, however, that the prosthetic device effects a rigid
securement to the remaining limb portion of the patient so that the
prosthetic bottom plate 40 moves with such limb stump, particularly
when the limb stump is moved in the normal process of walking.
The connection of the leg force receiving plate 30 to the
prosthetic bottom plate 40 is effected in such manner as to permit
limited, cushioned pivotal movement between such plates.
Preferably, at least four quadrilateraly spaced elastomeric plug or
cushion elements 50, 50b, 50c and 50d are provided intermediate the
plates 30 and 40. Two of such elastomeric cushions, 50a and 50b,
are mounted in laterally aligned relationship between the plate 30
and 40 by screws 51 and 29 which respectively traverse appropriate
holes 40a provided in the prosthetic bottom plate 40 and holes 30a
provided in the leg force transmitting plate 30 and engage
internally threaded inserts 53 in cushions 50a and 50b.
The remaining two elastomeric plugs or cushions 50c and 50d are
longitudinally aligned with the longitudinal central axis of the
artificial shoe 10. The forward cushion 50c is secured only to the
leg force receiving plate 30 by a bolt 54 which traverses a
radially disposed slot 30b provided in the plate 30 and engages an
internally threaded insert 55 in cushion 50c. Cushion 50c has only
abutting contact with the undersurface of the prosthetic bottom
plate 40. The provision of the radial slot 30b permits the radial
position of the forward cushion plug 50c to be selectively adjusted
to provide the desired amount of compression which of course is a
factor of the weight of the patient and the desired stride. For a
heavier patient, the position of the forward cushion plug is moved
forwardly in the slot 30b.
The rearmost cushion plug 50d is secured in depending relationship
to the prosthetic plate 40 by a bolt 56 which threadably engages an
internally threaded insert 53 integrally molded in the top of plug
50d. An internally threaded sleeve 57 is integrally molded in the
lower portion of the rearmost plug 50d and receives the top end of
a threaded plunger 60 which projects downwardly thru a radial slot
30c in plate 30 and then between the ankle plates 20 and 21 for
purpose to be hereinafter described. It will be noted that the
plunger 60 moves in a vertically inclined path as the artificial
foot 10 is moved through a step. Thus, as the artificial foot 10 is
moved to the position where the heel of the shoe 1 initially
strikes the ground or other walking surface, a maximum compressive
force is imposed on the rear cushion plug 50d and this results in a
downward shifting of the plunger 60. In the middle of the step,
when the weight is equally distributed along the sole plate 11, the
degree of compression imposed on the rearmost cushion plug 50d is
reduced and the depending plunger 60 moves upwardly. At the end of
the step, adjustable lock nuts 61 on plunger 60 engages the plate
30 to elevate the heel portion of the artificial foot 10.
In accordance with this invention, this shifting movement of the
depending plunger 60, which is a function of the relative pivotal
movement of the prosthetic bottom plate 40 with respect to the leg
force receiving plate 30 about a transverse horizontal axis, is
employed to effect the automatic latching and releasing of the toe
simulator 14 in the elevated position relative to the sole plate 11
in the proper sequence in the movement of the artifical foot
through a normal step. A friction type latch lever 70 is provided
which is of generally angular configuration and has one end thereof
pivotally mounted to the sole plate 11 for movement in a vertical
plane by virtue of having integral projections 70a and 70b enter
rectangularly shaped apertures 11m and 11n provided in the sole
plate 11 and engage the bottom of sole plate 11 to support lever 70
in cantilever fashion. One portion 70e of the lever 70 extends
upwardly between the arms 15d and 15e of the Ushaped control
linkage 15 and is provided with slots 70c and 70d which
respectively engage the arm portions 15d and 15e. The clearance
between the slots 70c and 70d and the arm portions 15d and 15e of
control rod 15 is limited by the relative angle between lever 70
and such arm portions so that the frictional engagement normally
tends to pivot the lever 70 in a clockwise direction and effect a
binding of such lever on the control rod arms 15d and 15e to
prevent the movement of the toe simulator 14 from its position
shown in FIG. 2 to the position shown in FIG. 1. However, a
counterclockwise rotation of the latching lever 70 will release the
frictional engagement of the lever slots 70c and 70d with the arms
15d and 15e of the control rod 15 and permit the control rod 15 to
slide freely forwardly to permit the toe simulator 14 to assume the
position shown in FIG. 1. Additionally, upward pivotal movement of
toe simulator 14 is not prevented by the frictional drag of
latching lever 70 on control rod 15.
The aforedescribed downward movement of the depending plunger 60 is
utilized to effect the counterclockwise pivoting of the latching
lever 70 to its control rod releasing position. Plunger 60 has a
generally U-shaped wire loop 80 loosely secured thereto between
washers 63 and nuts 64. The ends 80a of loop 80 are laterally
outturned to engage in holes 20k and 21k provided in ankle plates
20 and 21. The bight portion 81 of the force transmitting loop 80
moves upwardly and downwardly with the movement of the plunger 60.
Such bight portion is positioned in overlying engagement with the
nonpivoted end portions of the latching lever 70 and is effective
to rotate latching lever 70 in a counterclockwise direction
whenever the plunger 60 is depressed through the application of a
increased downward force to the rearmost cushion plug 50d.
The operation of the artificial foot embodying this invention
should clear to those skilled in the art from the foregoing
description. Briefly, the artificial foot 10 is longitudinally
adjusted to fit the patient's shoe in the manner heretofore
described by selecting an appropriate pair of adjustment recesses
20b and 21b in the ankle plates 20 and 21 for receiving the
transverse ends 24a and 24b of the instep plate support rod 24.
With the patient's shoe applied to the artificial foot, and
starting from rest position illustrated in FIG. 1, assume that the
other leg is first moved forward in a step. This results in the
artificial foot assuming the position illustrated in FIG. 2 wherein
nuts 61 engage the bottom of plate 30 to elevate the heel portion
of foot 10. The toe simulator portion 14 is pivoted upwardly or
counterclockwise with respect to the sole plate 11 against the bias
of the spring 16. Since the depending plunger 60 is in an elevated
position, the latching lever 70 frictionally engages the control
rod 15 to maintain the toe simulator 14 in the upturned position
illustrated in FIG. 2. As the artificial foot is then moved forward
in the course of performing its step, the toe simulator portion 14
remains in the upturned position shown in FIG. 2 and eliminates the
posibility of dragging of the shoe toe during this portion of the
step.
As the heel of the shoe 1 containing the artificial foot 10 strikes
the walking surface at the end of the step by the artificial foot,
the increased compressive force on the rear cushion plug 50d due to
the pivotal movement of the prosthetic bottom plate 40 relative to
the leg force receiving plate 30 causes a downward depression of
the plunger 60, and this in turn causes a counterclockwise rotation
of the latching lever 70 to release the control linkage 15 to
permit the toe simulator 14 to return to the position shown in FIG.
1.
Thus the operation of the artificial foot corresponds very closely
to that of a natural foot. In the event that the walking has to be
accomplished on an uneven surface, the multi-plane cushioned
pivotal movement of the prosthetic bottom plate 40 relative to the
leg force receiving plate 30 provided by the plurality of spaced
cushion plugs 50a, 50b, 50c and 50d permits the artificial foot to
accomodate such uneven terrain in much the same manner as a natural
ankle.
Modifications of this invention will be readily apparent to those
skilled in the art and it is intended that the scope of the
invention be determined solely by the appended claims.
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